Extrusion apparatus for thin-walled hollow tubing



Jan., 22, i957 A. KREIDLER 778,494

EXTRUSION APPARATUS FOR THIN-WALLED HOLLOW TUBING Filed nec. 17, 1952United States Patent Fice.

EXTRUSION APPARATUS FOR THIN-WALLED HOLLOW TUBING Alfred Kreidler,Stuttgart, Germany Application December 17, 1952, Serial No. 326,428Claims priority, application Germany December 31, 1951 1 Claim. (Cl.207-9) The invention concerns the production of hollow, especiallythin-walled bodies by forming. It is also concerned with the productionof a sleeve-shaped body, in which the material for the formation of thewall of the sleeve rises round the ram in the ow forming process(Becher-flow pressing) and it can also concern the forming by punchingof a hollow body by a ram in the die penetrating into the bar, or ahollow body with stranddike extensions by forming, in which the shell ofthe bar to be extruded remains as the wall of the hollow body, orfinally, any desired combination of two or all three of the abovepossibilities. The process according to the invention may be consideredfor hot forming and for cold forming.

ln all these processes there arises a difficulty that the press ram canonly be removed from the finished hollow body with diiiiculty. Thepresent invention seeks to overcome these difliculties.

It is, therefore, one object of the present invention to provide asubstantially thin disc, projecting over it-s frontal surface, on thepress ram which remains in Ithe hollow body as a lost disc after theforming operations; thereby then resulting in a certain play between theinner wall of the hollow body and the ram so that it can be extractedwithout effort.

The use of pressure discs of 'greater thickness, for example about 60mm. thickness, is known in itself. These consist of expensive heatresisting tool steel, as they are intended to be used for a large numberof pressing operations. For the present case, where the disc remains inthe formed part-i. e. is only used once-fairly thin thick-- nesses aresufficient and also the material need not be of such high value.

It is another preferred object of the present invention to provide a cap(sheet metal hood) over-lapping the ram with its edges which can be usedas the lost disc. In order to keep the disc or cap central with respectto the bar so that equal thickness of the wall may be obtained aroundthe hollow body, it is expedient to use a blank which is provided on itsfrontal surface turned towards the ram with a flat central shallow borefor the reception of the disc or cap.

It is still another object of the present invention to provide a disc ofsheet metal to be disposed in front of the ram, the edge of this discprojecting beyond the ram being flanged over the frontal edge of thepunch at the beginning of the pressing operation, like a cap.

As the thickness of the disc or cap mounted in front is generallycomparatively slight, it will be advisable for it to be cooled duringthe forming operation with a suitable cooling liquid fed and dischargedthrough the ram.

lt is therefore, still another object of the present inven- 2,778,494Patented*y J'a-n. 22', 1957' tion in which the ram, is expedientlyprovided onl its frontal surface-with coolingA grooves extendingspirally or radially, for example, into which longitudinal bores emptyfor the feeding and discharge of the cooling fluid.

With these and other objects in view which will become apparent in theyfollowing detailed description, the present invention Will be clearlyunderstood in connection with the accompanying drawings, in which:

Figure l is a longitudinal section through the relevant parts of aforming press at the beginning of the pressing operation, with the useof `a lost disc;

Fig. 2 is a similar view at a later stage at the same operation;

Fig. 3 is a view similar -to Fig. 2 but showing the use of a sheet metalhood instead of the flat disc; and

Figs. 4 and 5 are similar views showing the use of a round of sheetmetal mounted in front of the ram.

A cylindrical holder 1 of a forming press (Fig. l) is sealed oi by amatrix 2, which has a discharge aperture 3. A blank 4, which has ashallow central bore 6 on its frontal surface turned towards the ram 5,is inserted into the holder 1. A pressure disc 7 is inserted into thebore 6 so `as to be mounted in front of the ram 5. The ram has on itsfrontal surface radially extending cooling grooves 8 which communicatewith feeding and discharge channels 9 for the cooling liquid. Althoughthe feeding and passage channels 9 and cooling grooves 8 are shown inthe embodiment disclosed in Figs. 1 and 2 only, it is to be understoodthat such cooling grooves may be provided also in the ram 5 of Figs. 3to 5, disclosing the other two embodiments, described below.

When the ram 5 is lowered with the disc 7 (Fig. 2) on the one hand astrand-like extension 8 is forced through the aperture 3 of the matrix2, whilst on the other hand the wall 11 of the hollow body to beproduced remains in the holder. As a result of the difference indiameter between the disc 7 and the ram 5, a clearance 12 remainsbetween the latter and the remaining wall 11. This clearance allows ltheram 5 to be withdrawn immediately after the completion of the formingoperation, whilst the disc 7 remains in the pressed piece as a lostdisc.

In a variation (Fig. 3) a sheet metal hood 13 is mounted in front of theram 5 instead of the disc 7. The iiange 14 of this hood overlaps thefrontal edge of the punch. The thickness of the flange 14 determines theclearance 12 between the wall 11 and the punch S.

Finally, a deformable sheet metal disc or round plate 15 may be used(Fig. 4). This round plate is disposed in front of the ram 5; and thefront edge region 16 of the round plate 15 (Fig. 5) is anged backwardsduring the pressing to form a hood over the 4front edge of the ram.

While I have disclosed several embodiments of the present invention, itis to be understood that these embodiments :are given by example onlyand not in a limiting sense, the scope of the present invention beingdetermined by the objects and the claim.

l claim:

In a forming press for producing hollow workpieoes by pres-sing out thecore from solid main blanks by means of a relatively thin auxiliaryblank disposed on the face of the said main blank which is subjected topressure, a reciprocating ram having passages extending longitudinallytherethrough, grooves disposed in the front face of :the said ram, thesaid passages terminating into said grooves, the latter bearing againstthe said auxiliary blank, the said passages and grooves being adapted topass a cooling medium through the said ram for cooling the ram face andthe said auxiliary blank.

References Cited in the le of this patent UNITED STATES PATENTS BornNov. 14, 1933 Staples Feb. 18, 1936 Singer Mar. 31, 1936 Friden Nov. 21,1939 Hill Feb. 11, 1941 Poux Oct. 19, 1948

